The "10,000 Hour-Rule," the idea that becoming world-class in something requires 10,000 hours of dedicated practice, originated with K. Anders Ericsson and was brought to a huge audience by Malcolm Gladwell in his book Outliers.

One of Tim Ferriss' claims in his new book, The 4-Hour Chef, is that becoming world class can take much less time, less than six months if you use certain learning techniques.

Ferriss has a few specific quibbles with the 10,000 Hour Rule which he outlines in the book:

How you train can significantly change how much you get out of every hour.

The data which supports the rule tends to be from small samples, and is observational rather than experimental. That raises issues as to whether there's causation, or just correlation.

By inventing a different way to do the high jump, Dick Fosbury completely changed the scale and standard of how it was measured. An anomaly or giant leap forward can make you world class very quickly.

Technology makes a difference. Whether its the Internet, or even cameras that shoot video at many frames per second, the information and tools you have available make a huge difference, and accelerate learning.

It's also a matter of definition. Ferriss defines world class as being in the top five percent rather than the top 0.5 percent. The latter is often limited to people with incredible gifts and focus, but the former is attainable by almost anybody.

Sometimes generalists who haven't dedicated themselves to any one thing can be superior. Ferriss gives the example of Steve Jobs, who wasn't the world's best engineer or designer, but could connect things unlike anyone else.

The takeaway? Dedication and talent mean a great deal, but how you go about learning something can mean just as much. Technology, technique, and definition narrow the places where the 10,000 hour rule applies.